sd_bus_track_add_name(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | SEE ALSO | COLOPHON

SD_BUS_TRACK_ADD_NAME(3)  sd_bus_track_add_name SD_BUS_TRACK_ADD_NAME(3)

NAME         top

       sd_bus_track_add_name, sd_bus_track_add_sender,
       sd_bus_track_remove_name, sd_bus_track_remove_sender,
       sd_bus_track_count, sd_bus_track_count_sender,
       sd_bus_track_count_name, sd_bus_track_contains,
       sd_bus_track_first, sd_bus_track_next - Add, remove and retrieve
       bus peers tracked in a bus peer tracking object

SYNOPSIS         top

       #include <systemd/sd-bus.h>

       int sd_bus_track_add_name(sd_bus_track* t, const char* name);

       int sd_bus_track_add_sender(sd_bus_track* t,
                                   sd_bus_message* message);

       int sd_bus_track_remove_name(sd_bus_track* t, const char* name);

       int sd_bus_track_remove_sender(sd_bus_track* t,
                                      sd_bus_message* message);

       unsigned sd_bus_track_count(sd_bus_track* t);

       int sd_bus_track_count_name(sd_bus_track* t, const char* name);

       int sd_bus_track_count_sender(sd_bus_track* t,
                                     sd_bus_message* message);

       int sd_bus_track_contains(sd_bus_track* t, const char* name);

       const char* sd_bus_track_first(sd_bus_track* t);

       const char* sd_bus_track_next(sd_bus_track* t);

DESCRIPTION         top

       sd_bus_track_add_name() adds a peer to track to a bus peer
       tracking object. The first argument should refer to a bus peer
       tracking object created with sd_bus_track_new(3), the second name
       should refer to a D-Bus peer name to track, either in unique or
       well-known service format. If the name is not tracked yet it will
       be added to the list of names to track. If it already is being
       tracked and non-recursive mode is enabled, no operation is
       executed by this call. If recursive mode is enabled a per-name
       counter is increased by one each time this call is invoked, and
       sd_bus_track_remove_name() has to be called as many times as
       sd_bus_track_add_name() was invoked before in order to stop
       tracking of the name. Use sd_bus_track_set_recursive(3) to switch
       from the default non-recursive mode to recursive mode, or back.
       Note that the specified name is tracked as it is, well-known
       names are not resolved to unique names by this call. Note that
       multiple bus peer tracking objects may track the same name.

       sd_bus_track_remove_name() undoes the effect of
       sd_bus_track_add_name() and removes a bus peer name from the list
       of peers to watch. Depending on whether non-recursive or
       recursive mode is enabled for the bus peer tracking object this
       call will either remove the name fully from the tracking object,
       or will simply decrement the per-name counter by one, removing
       the name only when the counter reaches zero (see above). Note
       that a bus peer disconnecting from the bus will implicitly remove
       its names fully from the bus peer tracking object, regardless of
       the current per-name counter.

       sd_bus_track_add_sender() and sd_bus_track_remove_sender() are
       similar to sd_bus_track_add_name() and sd_bus_track_remove_name()
       but take a bus message as argument. The sender of this bus
       message is determined and added to/removed from the bus peer
       tracking object. As messages always originate from unique names,
       and never from well-known names this means that this call will
       effectively only add unique names to the bus peer tracking
       object.

       sd_bus_track_count() returns the number of names currently being
       tracked by the specified bus peer tracking object. Note that this
       function always returns the actual number of names tracked, and
       hence if sd_bus_track_add_name() has been invoked multiple times
       for the same name it is only counted as one, regardless if
       recursive mode is used or not.

       sd_bus_track_count_name() returns the current per-name counter
       for the specified name. If non-recursive mode is used this
       returns either 1 or 0, depending on whether the specified name
       has been added to the tracking object before, or not. If
       recursive mode has been enabled, values larger than 1 may be
       returned too, in case sd_bus_track_add_name() has been called
       multiple times for the same name.

       sd_bus_track_count_sender() is similar to
       sd_bus_track_count_name(), but takes a bus message object and
       returns the per-name counter matching the sender of the message.

       sd_bus_track_contains() may be used to determine whether the
       specified name has been added at least once to the specified bus
       peer tracking object.

       sd_bus_track_first() and sd_bus_track_next() may be used to
       enumerate all names currently being tracked by the passed bus
       peer tracking object.  sd_bus_track_first() returns the first
       entry in the object, and resets an internally maintained read
       index. Each subsequent invocation of sd_bus_track_next() returns
       the next name contained in the bus object. If the end is reached
       NULL is returned. If no names have been added to the object yet
       sd_bus_track_first() will return NULL immediately. The order in
       which names are returned is undefined; in particular which name
       is considered the first returned is not defined. If recursive
       mode is enabled and the same name has been added multiple times
       to the bus peer tracking object it is only returned once by this
       enumeration. If new names are added to or existing names removed
       from the bus peer tracking object while it is being enumerated
       the enumeration ends on the next invocation of
       sd_bus_track_next() as NULL is returned.

RETURN VALUE         top

       On success, sd_bus_track_add_name() and sd_bus_track_add_sender()
       return 0 if the specified name has already been added to the bus
       peer tracking object before and positive if it hasn't. On
       failure, they return a negative errno-style error code.

       sd_bus_track_remove_name() and sd_bus_track_remove_sender()
       return positive if the specified name was previously tracked by
       the bus peer tracking object and has now been removed. In
       non-recursive mode, 0 is returned if the specified name was not
       being tracked yet. In recursive mode -EUNATCH is returned in this
       case. On failure, they return a negative errno-style error code.

       sd_bus_track_count() returns the number of names currently being
       tracked, or 0 on failure.

       sd_bus_track_count_name() and sd_bus_track_count_sender() return
       the current per-name counter for the specified name or the sender
       of the specified message. Zero is returned for names that are not
       being tracked yet, a positive value for names added at least
       once. Larger values than 1 are only returned in recursive mode.
       On failure, a negative errno-style error code is returned.

       sd_bus_track_contains() returns the passed name if it exists in
       the bus peer tracking object. On failure, and if the name has not
       been added yet NULL is returned.

       sd_bus_track_first() and sd_bus_track_next() return the
       first/next name contained in the bus peer tracking object, and
       NULL if the end of the enumeration is reached and on error.

   Errors
       Returned errors may indicate the following problems:

       -EUNATCH
           sd_bus_track_remove_name() or sd_bus_track_remove_sender()
           have been invoked for a name not previously added to the bus
           peer object.

       -EINVAL
           Specified parameter is invalid.

       -ENOMEM
           Memory allocation failed.

NOTES         top

       These APIs are implemented as a shared library, which can be
       compiled and linked to with the libsystemd pkg-config(1) file.

SEE ALSO         top

       systemd(1), sd-bus(3), sd_bus_track_new(3)

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
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       This page was obtained from the project's upstream Git repository
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systemd 249                                     SD_BUS_TRACK_ADD_NAME(3)

Pages that refer to this page: sd-bus(3)sd_bus_track_new(3)